An experiment was carried out in a small block of mixed bush in Tanganyika in an attempt to eliminate the two resident species of tsetse fly. Glossina morsitans Westw. and G. suynnertoni Aust., by means of bait cattle treated with DDT. Small cattle were used at the rate of 100 per square mile in herds of 12 or 13 per one-eighth of a square mile. Their numerical superiority over the large game was no more than about 3: 1.

The cattle were sprayed twice weekly. Originally a 10 per cent. suspension of the p.p′isomer was prepared from a commercial formulation of DDT. Later a laboratory-prepared emulsion (10 per cent. technical DDT) was used.

Extermination was expected with a reduction in numbers of old male tsetse of 99·9 per cent. In practice G. morsitans was reduced by 99·5 per cent. and G. swynnerloni by 92·5 per cent.

It is considered that there was sufficient immigration across the barrier clearing to account for the failure to achieve extermination of either species. It is not possible to say if extermination would have been attained in the absence of immigration.

It is considered that with the insecticidal formulations now available there is not much prospect of improving on these results in similar conditions although a great reduction in tsetse numbers is possible and might stop the carrying of disease. In the dry season, after the grass has been burnt, there is better prospect of success.

Aëdes (Stegomyia) polynesiensis Marks, Culex (Culex) pipiens fatigans Wiede-mann and Culex annulirostris Skuse were collected at Aitutaki, Southern Cook Islands, during a brief visit in 1958. Possible means of introduction of these mosquitos are discussed.

The life-history and bionomics of the Coreid bug, Theraptus sp., which causes premature nutfull of coconuts in Zanzibar, were studied in the laboratory and in the field.

From the various experiments carried out it is concluded that:—

The development of the insect from the egg to the adult took from 26–39½ days depending on temperature and the food available.

The average length of life of the female is 45 days during which time she may produce over 100 fertile eggs.

The primary host-plant of Theraptus is the coconut palm, but the bug readily infests mango, guava, cinnamon and cacao trees when they are fruiting.

The pest will attack and develop successfully on nuts from the newly emerged to the mature ones.

Agents which exert a measure of biological control include the tree-nesting ant, Oecophylla longinoda (Latr.), an internal Strepsipteran parasite, an unidentified Reduviid, two unidentified Hymenopterous egg-parasites and possibly some small ant species which prey on the eggs. Of these, only the ant, O. longinoda, is capable of giving complete protection to the palm which it occupies.

Theraptus sp. from Zanzibar, Pemba and Tanganyika have been inter-bred.

Individuals of the F1 generation are fertile, but a partial sterility in some crosses may exist.

It is concluded that there is only one species but possibly three varietal strains.

Field observations on the Culicidae of Sardinia and Corsica were undertaken in 1944, during the period 1946 to 1950, and again in 1952. A total of 52 species are recorded as being present, 46 of which are known from Corsica and 35 (exclusive of Dixinae) from Sardinia. The faunal list of the latter island has been increased by 20 new records and that of Corsica by three. The total number of species by genus is as follows: Dixa (7), Chaoborus (3), Anopheles (12), Uranotaenia (1), Culiseta (6), Orthopodomyia (1), Taeniorhynchus (2), Aëdes (12), and Culex (8).

The previously unknown male of Taeniorhynchus buxtoni Edwards is described from Sardinian material. Culiseta litorea (Shute), heretofore known only from England, was found in two localities in Sardinia. Aëdes vittatus (Bigot) was rediscovered in Corsica, 83 years after its original description.

Keys are given to subfamilies, genera and species. Critical notes on species differentiation are included and biological characteristics briefly discussed.

Experiments were carried out in Syria with parathion dusts for the control of Eurygaster integriceps Put. on wheat to ascertain the best time to apply the dust and the most suitable rate of application using a 6 h.p. dusting machine mounted on a “ jeep ”.

A field experiment is described in which a dust containing 0·75 per cent. parathion was applied under a drag-sheet to three plots of wheat at rates of 40, 20 and 10 kg. per hectare, respectively. The insects onthe wheat were mostly in the first three instars and the population was assessed by making 100 hand sweeps with a net at both 60 hours and 70 hours after treatment on each plot. The effect of treatment when compared with a control plot was to reduce the insect population in the three plots by 98·4 per cent., 83 per cent. and 65 per cent., respectively.

A further field experiment on a larger scale was carried out in an area in which plots of wheat were interplanted with plots of barley. In this case, the great majority of the insects were fourth-stage nymphs or adults. Five plots of wheat were treated with a dust containing 0·8 per cent. parathion at a rate of 35 kg. per hectare without using a drag-sheet. In two of the plots which were dusted in calm weather, about 89 per cent. control was obtained, in the other plots the effectiveness of the dusting was appreciably reduced by wind.

A cage containing 1,406 live specimens was placed, prior to dusting, in one of the plots of the latter experiment (dusted under calm conditions) and 6¾ hours after treatment all were dead. In the control only two specimens out of a total of 239 originally caged were found dead 24 hours later.

Glossina brevipalpis Newst. is recorded for the first time in Ruanda-Urundi, where it has been found in the riverine forest of the upper Malagarasi river in the south-east of the territory.

Resting places of both male and female flies have been found to be on tree trunks, between six and twelve feet up, in heavily shaded riverine thickets.

The species is clearly crepuscular. It is suggested that the male's habit of resting on paths toward sunset is due to thermotropism rather than to phototropism, or that it may be related to passage of game.

Numerous puparia have been found in a late-dry-season breeding ground; these have hatched readily.

The animals encountered near the habitat of G. brevipalpis.

Infections by trypanosomes have been found in proboscis, gut and salivary glands, but experiments on transmission of these trypanosomes from the wild flies to goat, guineapig and rabbit have thus far failed. Research is at present being carried on to determine the nature of the trypanosomes, of which there are probably several.

Laboratory investigations with the mosquito AËdes aegypti (L.) have shown that air pressure has the following effects on flight activity:

The effects of pressure changes are consistently large enough to constitute an important factor in determining activity provided the mosquitos are acclimatised first to a particular pressure level.

The period of constant conditions necessary for complete acclimatisation was between three and six hours for all pressure conditions investigated.

When the period of acclimatisation had been fulfilled, the flight activity was approximately the same at all levels of static pressure investigated between 550 mm. and 800 mm. Hg.

After complete acclimatisation the activity following a moderate decrease in pressure was 1·5 to 2·4 times that following a similar increase in pressure when the general pressure level exceeded 735 mm. Hg.

When the general pressure level was less than 735 mm. Hg., the activity following a decrease in pressure was less than that following an increase; it would appear that 735 mm. is a critical pressure level for the stock of A. aegypti employed.

The activity during a uniform rise in pressure from 530 mm. to 730 mm. at 7·7 mm. /min. was at least 10 times that during a reverse fall in pressure fall in pressure at the same uniform rate.

Provided the rate of change was not greater than 1 mm./sec., the maximum flight activity for falling pressures was observed at 780 mm. while the maximumfor rising pressures was observed at 735 mm.

Experiments were designed to determine the criteria by which an ovipositing female of Spalangia drosophilae Ashm. is attracted to an environment where suitable hosts may be found, and by which these hosts are selected.

The results obtained indicate that ovipositing female Spalangia are attracted to and maintained in areas where suitable host puparia may occur by their reaction to sensory impressions. Thus females tend to be attracted to dampness and to soil level where, in grasses, host material is likely to be found. In such an area searching for hosts appears to be at random, but once an object that is a possible host is located there follows a careful examination and, if the object is “ considered ” a suitable host, oviposition follows. It appears that there are several definite criteria by which an object is accepted as a host suitable for oviposition. In general the hosts selected by the parasite are those which are suitable for the development of her progeny.

The weight of fresh grass eaten by Schistocerca gregaria (Forsk.) on each day of its development from hatching until maturation of the adults was investigated. Hoppers in all instars ate on the average about one gram per gram body-weight per day on the middle days of the instars and the adults ate approximately half-a-gram per gram body-weight each day. The percentage of food assimilated, calculated from the dry faeces and estimated dry weight of food eaten, falls from about 78 in the first to 35 in the fifth instar. There were some indication that the food consumption per hopper increases with the number of hoppers per cage.

The weight of wheat bran eaten by hoppers was also investigated. The amount eaten by hoppers on the middle day of the first instar is approximately the same, in relation to their body weight, as that eaten per day just before and just after moulting by those in the fourth and fifth instars. More is eaten in the middle of these instars.

Measurements of weights and lengths of males and females in the hopper instars and of the weights of adults showed that in the course of their development females become progressively heavier and larger than males. The weight of a newly-hatched hopper is about 10 mg.; a female fledgling weighs about 2 gm. and a male 1·5 gm. Hoppers are approximately 1 cm. long on hatching, and males on reaching maturity are about 4·5 cm. long and females about 5.0 cm.

The larva of Apomecyna binunila Pasc. is a stem-borer of cucurbits in South Africa and the Sudan. In the latter country its known distribution lies between the 12° and 20° parallels of latitude. A description of the morphology of adult, larve and pupa is given. Observations on the life-history reveal a very short development period of approximately 35 days from oviposition to adult emergence. The host range is restricted to sweer and water melon. Damage is only serious where larval populations are high and the vascular tissues are destroyed. With smaller infestations (two to three larvae per 10 cm. of stem) vascular continuity is not seriously interrupted. Reference is made to Iphiaulax sp. (BRACONIDAE), the first record of a parasite from this beetle. The larva is parasitic on larvae of Apomecyna.

Glossina palpalis fuscipes Newst. was studied in lake-side forest in north-east Lake Victoria and in riverine forest on the Kuja river, which runs into Lake Victoria. Climatic records are given. Trees counts were made in fifty acres of lake-side forest.

Populations of G. palpalis exhibit long-term fluctuations which are not annual and not related to season. On the lake shore, the density of G. palpalis is roughly correlated with the width of the forest, being least where the forest is narrow. In a block 2,200 yeards along the shore by 100 yards wide (this was the widest forest studied) the population was 4,600 non-teneral males. The mean catch along the 2,200 yards of shore was 78 non-teneral males. Calculated on an area basis, this is more than ten times the population which would be inferred from the same catch of G. morsitans or G. swynnertoni. The mean death-rate in this isolated block was 26 per cent. per week, and the mean length of life was 27 days.

Analysis of catches indicates that riverine G. palpalis are always more hungry than those on the lake shore, for the percentages of tenerals, of females, and of males attacking, are all higher on the river. Catches from a boat produce more females but fewer males than land catches. Carrying a screen produced more females on some occasions, but not on others, the discrepancy being unexplained.

Conclusions concerning the distribution and field habits of Anthrenus verbasci (L.), A. fuscus Ol. and A. museorum (L.), are based upon the results of three surveys.

The first survey comprised the collection of adults of Anthrenus from attractive flowers, e.g., hogweed, Heracleum sphondylium, in various localities furing June and July. This showed that:—

A. Verbasci occurred in large numbers only in the suburban areas of south-east England, extending also to the west along the south coast.

A. fuscus was generally distributed in all types of locality in the south reaching a peak abundance in the vicinity of farms. Its members diminished rapidly towards the north.

A. museorum occurred in small numbers only, often accompanying A. fuscus.

The second survey comprised the collection of larvae from natural habitats and included results from an earlier survey of certain birds' nests. This showed that:—

A. verbasci was characteristically an inhabitant of dry birds' nests.

A. fuscus was usually found feeding on dead insects around spiders' webs, under the bark of trees, etc.

A. museorum occurred in small numbers in company with A. fuscus.

The habitat difference between A. verbasci and A. fuscus was sharply defined. Only very rarely was one sspecies found in the habitat typical of the other.

An experiment is described where applications of a coarse aerosol were made to savannah woodland containing the tsetse flies, Glossina moritans Westw., G. swynnertoni Aust. and G. pallidipes Aust.

Seven applications were made, each at a nominal dosage of 0·25 lb. of technical DDT per acre and 0·25 gallons of solution per acre. The applications in any particular part of the treaed woodland covered an interval of 90 days, or rather more than two pupal periods.

The coarse aerosol was produced by emitting the insecticidal solution under pressure through fine nozzles fitted to a boom. It had a mass median diameter of approximately 60 microns, and droplet dismeters varied from a few microns to approximately 200 microns.

The population of G. pallidipes was so drastically reduced that it has subsequently dies out. The reduction of G. morsitans was approximately 95 per cent. The differences between the reductions are attributed mainly to differences between the ease with which the three species can be killed. It is pointed out that this is not necessarily equivalent to differences in susceptibility.

Comparisons are made with previous experiments, and the different results of the various experiments are difficult to explian satisfactory. The increased cover in savannah areas during the leafy period may have reduced the effectiveness of the applications, and the total periods covered by the various series of applications were probably also important. Random effects, leading to ineffective treatments, may also be important.

Costs are discussed.

The “ North Block ” at Kikore, Central Province, Tanganyika, was treated with insecticide dispersed from an Anson 1 aircraft during the period 23rd January to 4th May 1951. The area consisted of some 4,000 acres of mixed bush, including about 230 acres of miombo, infested by two species of tsetse fly, Glossina morsitans Westw. and swynnertoni Aust.

The insecticide used was equivalent to a 19·4 per cent. solution of technical BHC (equal to 2·45 per cent. γ isomer) in 50 per cent. diesel oil, 50 per cent. power kerosene. The solution was dispensed through a boom and nozzles under pressure as a coarse aerosol (mass median diam. 70 microns), at a nominal mean dose of 0·25 lb. technical BHC per acre per application. Eight applications were planned and seven completed.

The first application was relatively ineffective, and for the second and subsequent cycles the emission rate was increased and over part of the block the swathe width was reduced. The result was a much improved kill but neither species of tsetse was exterminated.

Owing to the number of factors involved, it is not possible to give any principal reason why this experiment was less successful than previous ones, but many of the difficulties encountered are inherent in rainy-season operations in East Africa.

An isolated area of 2,200 acres of thicket and thronbush in the Central Province, Tanganyika, was treated from the air with a DDT-in-oil aerosol in an attempt to eliminate the tsetse fly, Glossina swynnertoni Aust. Eight applications of 0·25 lb. technical DDT per acre were planned to be done at fortnightly intervals.Delays due to unseasonal bad weather reduced this to seven at a slightly higher rate and over a longer-period.

G. swynnertoni was reduced from an apparent density of about 7 to zero at the end of the second application. No flies were caught after the fifth application for a period of six months.

It is not possible to say whether the few caught since then have been brought in or are the offspring of survivors of the insecticidal treatment.

This experiment was more successful than that on the Galapo Block in the same ares, to a highly significant degree, and this is attributed to the vulnerability of the smaller population present. It was doubtfully better than the first treatment of the North Block, also in this area, because the increase in population in the latter block may have been assisted by immigration.

Both p, p′DDT and a sample of commerical DDT have been compared with γ BHC as insecticides acting in the vapour phase. Both the direct fumigant action of the insecticides and the toxicity of the vapours sorbed on to stored products have been examined. After storage in atmosphere saturated with the vapours for six months, wheat retained sufficient of all three insecticides to control adults of Calandra graria (L.) and inhibit the develpment of larval Sitotroga ceraalella (Ol.). This control and inhibition was complete for BHC, and stronger for commercial than for p, p′DDT. Similar results were obtained when the insecticides sorbed on flour were tested using the eggs or larvae of Tribolium confusum Duv., or when fumigated groundnut kernels were tested against T. confusum, but such groundnut produced little toxic action against Oryzaephilus surinamensis (L.).